and a mena mississippi senator. federal agents say, they have arrested 45 year-old paul kevin curtis of mississippi. the deadly substance inside those letters is known as ry-sin. both letters were intercepted at screening facilities, and both were postmarked memphis tennessee--april 8th. the white house says, staffers followed a careful drill and handling the letters, and no one was injured. >> the u.s. senate has blocked a proposal to expand background checks on gun sales. the plan failed to get the 60 votes needed to pass. the move sparked anger from president obama and disappointment from the parents of schoolchildren who were massacred just four months ago in newtown, connecticut. >> congresswoman gabrielle giffords, who was severely injured in gun violence, also stood by the president's side, if she is quoted as being furious that the measure did not pass and accused the opposing senators of " cowardice ". the final vote tally was 54 to 46. the proposal was part of a compromise that was struck by a democratic a